Anatomical Structure of Ectomycorrhiza in Abies sibirica Ledeb. and Picea obovata Ledeb. under Conditions of Forest Ecosystems Polluted with Emissions from Copper-Smelting Works

Changes in the anatomical characters of ectomycorrhiza in Siberian fir and Siberian spruce were studied in natural forests polluted with heavy metals (Cu, Zn, Cd, Pb, As, and Fe) and sulfur dioxide. As technogenic load increased, the total radius of mycorhiza terminals and plant roots included in them increased in the organic horizon and decreased in the mineral part of the soil. The absolute thickness of fungal mycorhiza caps and their relative contribution to the total volume of consuming organs increased under pollution. The observed responses were regarded as adaptive, aimed at compensating the adverse effects caused by technogenic pollution.     

The structure of absorbing roots in invasive and native maple species

Specific structural features of absorbing roots have been studied in Acer negundo (an invasive species in the southern Cisural region), compared to native Acer platanoides and A. tataricum. A comparative analysis of the diameter of fine roots, stele and bark volumes, and the frequencies of roots with retained primary bark, root hairs, arbuscular mycorrhiza, and dark septate endophytes has been performed in the invasive and native species from four habitats (by two habitats in the forest–steppe and steppe zones). The roots of A. negundo have been additionally studied in trees from two monospecific stands. It has been found that the structure of fine roots significantly differs between the invasive and native species: the roots of A. negundo are larger, with relatively poorly developed root hairs and low occurrence of dark septate endophytes. In monospecific stands, the frequency of mycorrhiza in A. negundo roots is very low, with arbuscules and dark septate endophytes being totally absent. It is concluded that specific structural features of the belowground absorbing apparatus in A. negundo are accounted for mainly by traits autonomously formed in a plant, rather than by characteristics of symbiotic relationships, and that they are not consistent with the assumption that the invasive species can utilize soil resources more effectively or more rapidly than taxonomically close native species.     

Cadmium Concentration in Vegetables Grown on Urban Soils Irrigated with Untreated Municipal Sewage

Cadmium (Cd) is considered as a potential toxin that is principally dispersed in natural and agricultural environments through anthropogenic sources. Untreated municipal sewage, often a potential source of Cd, is generally used to irrigate urban agricultural soils in many developing countries. A study was carried out to determine Cd concentration in untreated municipal sewage and sewage-irrigated soils and vegetables. The metal ion concentration in municipal sewage was found 3-fold (0.03mgL^–1) its permissible concentration in irrigation water (0.01mgL^–1). Ammonium bicarbonate–diethylene triamine pentaacetic acid NH₄HCO₃–DTPA) extractable Cd concentration in top 0.15m soil ranged between 0.25 and 0.34mgkg^–1. Soil Cd concentration was significantly correlated with soil clay content, pH, electrical conductivity, and cation exchange capacity. Cadmium availability index (CDI) decreased with an increase in soil depth. The metal ion was found in leaf (0.17–0.24mgkg^–1 fresh weight) and fruit (0.07–0.18mgkg^–1 fresh weight) portions of all the sampled vegetables: bitter gourd (Momordica charantia L.), cauliflower (Brassica oleracea L.), eggplant (Solanum melongena L.), fenugreek (Trigonella foenumgraecum L.), okra [Abelmoschus esculentus (L.) Moench], onion (Allium cepa L.), pumpkin (Cucurbita pepo L.), and spinach (Spinacia oleracea L.). Leafy tissue accumulated Cd about twice that of the fruit portion. Our results suggest that prolonged ingestion of sewage-irrigated leafy vegetables can develop such Cd levels in human body that may cause a number of illnesses.     

Total soil available nitrogen under perennial grasses after burning and defoliation

Total soil available nitrogen concentrations (NO^–3 + NH ₄ ⁺ ) were determined underneath plants of the more-competitive Poa ligularis, mid-competitive Nassella tenuis and the less-competitive Amelichloa ambigua exposed to various combinations of controlled burning and defoliation treatments. Defoliations were at the vegetative (V), internode elongation (E) or both developmental morphology stages (V + E) during two years after burning in northeastern Patagonia, Argentina. Hypotheses were that (1) concentrations of total soil available nitrogen after burning are greater underneath burned than unburned plants. With time, these differences, however, will gradually disappear; (2) greater total soil available nitrogen concentrations are underneath plants of the more- than less-competitive perennial grasses; and (3) total soil available nitrogen is similar or lower underneath plants defoliated at the various developmental morphology stages in all three study species than on untreated controls at the end of the study. Concentration of total soil available nitrogen increased 35% (p < 0.05) on average after the first six months from burning in comparison to control plants. However, these differences disappeared (p > 0.05) towards the end of the first study year. Total soil available nitrogen concentrations were at least 10% lower underneath the less competitive N. tenuis and A. ambigua than the more competitive P. ligularis on average for all treatments, although differences were not significant (p > 0.05) most of the times. Defoliation had practically no effect on the concentration of total soil available nitrogen. Rather than any treatment effect, total soil nitrogen concentrations were determined by their temporal dynamics in the control and after the experimental fire treatments.     

Estimating ‘rhizosphere priming effect’: Comparison of the indirect <Emphasis Type="Italic">y</Emphasis>-intercept regression approach and direct bare plot Approach

Determined the contribution of root derived CO₂ efflux to total CO₂ efflux (including root and non-root derived CO₂ efflux) is import to grope the mechanism of CO₂ efflux, however, becaused of ‘rhizoshere priming effect’ (RPE), it is difficult to achieve in practice. In this study, we attempted to estimate the RPE via comparing basal soil respiration (R_b) achieved by two different methods namely, y-intercept regression and direct bare plot approach in an arid cotton field, central Asia. On the basis of the y-intercept of linear regressions between below-ground respiration (BGR) and root biomass, R_b was indirectly calculated. Comparing with the first approach, the second approach involved direct measurements of soil respiration from bare plots. R_b estimated by y-intercept method contained the component of RPE whereas direct bare plot did not. We found that RPE showed a phenological trend with highest value in flowering stage at 0.145 g CO₂ m^–2 h^–1 and lowest at budding stage (0.007 g CO₂ m^–2 s^–1), even after the data had been corrected for the influence of soil temperature. We concluded that RPE needed to be considered when R_b was estimated by y-intercept approach.     

Ecology of Nuclear Polyhedrosis Virus in Western Siberian Populations of the Gypsy Moth (<Emphasis Type="Italic">Lymantria dispar</Emphasis> L.)

The impact of the nuclear polyhedrosis virus on the population dynamics of the gypsy moth Lymantria dispar L. has been studied. The results have shown that polyhedrosis morbidity in the western Siberian population of the insect is relatively low, compared to that reported for North American and European populations. A possible cause of this situation is found in the high migration activity of moths in the Asian L. dispar populations, which allows the virus load on the biotope to remain relatively stable and insufficient for the initiation of mass viral diseases during population outbreaks.__________Translated from Ekologiya, No. 3, 2005, pp. 222–226.Original Russian Text Copyright © 2005 by Ilinykh.     

Structure and formation of conifer stands in the upper timberline ecotone on the North Chuya Ridge,Central Altai

The structure of Siberian stone pine (Pinus sibirica Du Tour.) and Siberian larch (Larix sibirica Ledeb.) stands and specific features of their formation have been studies in the forest-tundra ecotone on the North Chuya Ridge (2235–2475 m a.s.l.). Changes in the structure of these stands along the transition from the upper boundary of closed forests to the high-mountain tundra have proved to have an ambiguous pattern. Both tree species form mixed clusters of similar-aged trees in the lower part of the ecotone but grow singly, in scatters, in its upper part. The formation of conifer stands (tree clusters) in the lower part of the ecotone, on the slopes of the Aktru River valley, began during climate warming in the second half of the 19th century. The expansion of confers to its upper part took place markedly later, in the early 20th century (Siberian larch) or even in the 1930s (Siberian stone pine).     

Climate change driven plant–metal–microbe interactions

Various biotic and abiotic stress factors affect the growth and productivity of crop plants. Particularly, the climatic and/or heavy metal stress influence various processes including growth, physiology, biochemistry, and yield of crops. Climatic changes particularly the elevated atmospheric CO₂ enhance the biomass production and metal accumulation in plants and help plants to support greater microbial populations and/or protect the microorganisms against the impacts of heavy metals. Besides, the indirect effects of climatic change (e.g., changes in the function and structure of plant roots and diversity and activity of rhizosphere microbes) would lead to altered metal bioavailability in soils and concomitantly affect plant growth. However, the effects of warming, drought or combined climatic stress on plant growth and metal accumulation vary substantially across physico–chemico–biological properties of the environment (e.g., soil pH, heavy metal type and its bio-available concentrations, microbial diversity, and interactive effects of climatic factors) and plant used. Overall, direct and/or indirect effects of climate change on heavy metal mobility in soils may further hinder the ability of plants to adapt and make them more susceptible to stress. Here, we review and discuss how the climatic parameters including atmospheric CO₂, temperature and drought influence the plant–metal interaction in polluted soils. Other aspects including the effects of climate change and heavy metals on plant–microbe interaction, heavy metal phytoremediation and safety of food and feed are also discussed. This review shows that predicting how plant–metal interaction responds to altering climatic change is critical to select suitable crop plants that would be able to produce more yields and tolerate multi-stress conditions without accumulating toxic heavy metals for future food security.     

Lipid peroxidation rates in <Emphasis Type="Italic">Taraxacum officinale</Emphasis> Wigg. and <Emphasis Type="Italic">Vicia cracca</Emphasis> L. from biotopes with different levels of soil pollution with heavy metals

The rates of lipid peroxidation (LPO) have been studied in Taraxacum officinale Wigg. (Asteraceae) and Vicia cracca L. (Fabaceae) from urban ecosystems with different levels of soil pollution with heavy metals (HMs), including Pb, Zn, Cu, and Cr. The former species responds to the increased HM contents by intensification of LPO processes, with their parameters correlating with the concentrations of Pb, Zn, and Cu in the soil. In the latter species from the same biotopes, conversely, LPO homeostasis remains actually undisturbed.     

Spatial Distribution of Animals and Variation in Their Trophic Activity Measured Using the Bait-Lamina Test in Sod-Podzolic Soil under a Spruce Forest

The mode of spatial distribution of soil animals and their trophic activity was studied in the sod-podzolic soil under a spruce forest. At the test point level, no apparent relationship between the distribution of soil animals and physicochemical characteristics of the soil was observed. The patterns of distribution of detritophages and the trophic activity (measured using the bait-lamina test) were similar. The perforation of laminae in the bait-lamina test resulted from the trophic activity of both micro- and mesofauna.     

Tree Ontogeny and Its Reflection in the Structure and Dynamics of Plant and Soil Covers

Based on the results of our own long-term experiments and the analysis of published data, the process of individual development (ontogeny) of trees and the parameters of ontogenetic stages are described. Changes in the environment-forming (edificatory) role of a tree in the course of ontogeny and upon its completion are characterized. The performance of this role leads to the formation of the following components of biogeocenosis heterogeneity: phytogenic fields of trees, gaps in the tree canopy, and windfall–soil complexes. The data concerning the interrelation of structural transformations of the plant and soil covers in the course of forest vegetation and soil formation on the primary substrate are reviewed.     

Minimal models and agroecological policy at the regional scale: An application to salinity problems in southeastern Australia

A minimal dynamical systems model that couples agricultural activity, native vegetation, and hydrological processes is developed to explore policy options regarding regional-scale soil and water salinization in southeastern Australia. The analysis suggests that although considerable revegetation is required to restore catchment water balance, the current value of water in uses other than agriculture is too low for revegetation to be economically viable. In contrast, groundwater pumping generates significant short-term gains by preventing soil salinization but is not a viable long-term solution. Thus, effective salinity management policy must include mechanisms to increase the value of water in uses other than irrigated agriculture to achieve sufficient long-term revegetation. These results are robust over a wide range of parameter values and thus provide a basis for policy action in the face of uncertainty about groundwater flow characteristics.     

Carbon dioxide exchange in the photosynthetic apparatus of trees in a mature spruce phytocenosis of the northern taiga subzone

Carbon dioxide exchange was studied in the photosynthetic apparatus of Siberian spruce (Picea obovata Ledeb.), Siberian larch (Larix sibirica Ledeb.), and weeping birch (Betula pendula Roth.) in a mature spruce forest. Parameters of CO₂ balance in different weather were characterized quantitatively on the basis of daily measurements of CO₂ exchange in needles and leaves of woody plants. The percent ratios of the components of carbon balance in needles and leaves of woody plants depending on daily photosynthetic fixation of carbon were determined. In summer, trees consumed 210 kg CO₂/ha (57 kg C/ha) in variable weather and 117 kg CO₂/ha (32 kg C/ha) in cloudy weather. Species specificity of CO₂ consumption was revealed, and the effects of environmental factors on the assimilatory activity of trees were determined.     

Behavior and analysis of Cesium adsorption on montmorillonite mineral

The adsorption of Cs by montmorillonite and the effects of experimental conditions on adsorption were investigated by using ¹³⁴Cs as a radioactive tracer. Additionally, the Cs-adsorbed and the modified montmorillonite were analyzed by X-ray Diffractometer System (XRD) and Scanning Electron Microscopy (SEM). The results showed that the adsorption of Cs by montmorillonite was efficient in the initial concentration (C₀) of 30 μg/L Cs nitrate solution with 20 g/L montmorillonite at room temperature. In this condition, more than 98% Cs⁺ ions could be adsorbed at pH 8. The adsorption equilibrium was achieved within 5 min and the relationship between the concentration of Cs⁺ in aqueous solutions and adsorption capacities of Cs⁺ can be described by the Langmuir adsorption isotherm. The adsorption rate would decrease when temperature increase from 0 °C to 50 °C or in presence of coexistent K⁺, Na⁺ and Ca²⁺, while modification by (NH₄)₂SO₄, [Ag(NH₃)₂]⁺, [Cu(NH₃)₄]²⁺ or 450 °C could improve the adsorption abilities of montmorillonite for Cs⁺. However, more than 89% of adsorbed Cs⁺ on montmorillonite could be desorbed by 2 mol/L HNO₃ solutions. The XRD and SEM analysis further showed that the structure of the Cs-adsorbed or modified montmorillonite were different from that of the original one.     

Biological sources of soil CO2 under Larix sibirica and Pinus sylvestris

Mycorrhizal ingrowth collars were used to study the effect of tree species on the seasonal dynamics of carbon dioxide flux from three major sources of soil respiration: (1) plant roots, (2) mycorrhizal hyphae, and (3) microorganisms. Distinct seasonality in carbon transport to mycorrhizae was revealed, with its highest values being observed during the second half of the growing season. The annual amount of C transferred through mycorrhizae did not differ between the two tree species, and the contribution of mycorrhizae to soil surface CO₂ emission was about 20%.     

Ecological characteristics of Alhagi sparsifolia Shap. seedling roots under different irrigation treatments

An trench profile method was used to study seasonal variation of root ecological characteristics of Alhagi sparsifolia Shap. seedlings under different irrigation treatments. The results indicated the following: (1) Root morphology: under excellent soil moisture conditions, A. sparsifolia seedlings developed many horizontal roots and root sprouts to compete for light; but under poor soil moisture, the vertical root system expanded its resource space into deeper soil. Plasticity of root morphology is an important strategy to capture water and adapt to the hyperarid environment. (2) Root/shoot ratio: root/shoot ratio increased with declining soil moisture, and this trend was more obvious later in the growing season. Increase of root/shoot ratio is a strategy for adapting to drought. (3) Growth of root system: The seedlings prefer to develop roots in shallower surface layers with less water availability. The growth depth and vertical growth rate of roots increased with decreased soil moisture. (4) Accumulation of root biomass: biomass and surface area of the root system decreased with increased soil depth, with the roots distributed in an ??inverted pyramid?? in vertical section view. The formation of root biomass conformed to a logistic ??slow-quick-slow?? growth curve, and total biomass decreased with intensity of soil drought. The findings will provide data useful for effective restoration of A. sparsifolia and better utilization of water resources in hyperarid regions.     

Changes in soil microbiota under the effect of acrylonitrile in a model experiment

A laboratory experiment was performed to evaluate the effect of acrylonitrile (20, 200, and 2000 mg/kg soil) on the abundance and structure of soil microbial community. The results of direct inoculation showed that acrylonitrile at 200 mg/kg stimulated the development of nitrile-utilizing prokaryotes, whereas at 2000 mg/kg it inhibited all test groups of microorganisms, including nitrile- and amide-utilizing bacteria. According to real-time PCR data, representatives of α- and ß-Proteobacteria were the most labile members of the soil microbial community, while Bacteroidetes and Fungi proved to be highly resistant to the effect of the pollutant.     

Analysis of the soil water balance for large-scale reforestation with <Emphasis Type="Italic">Eucommia ulmoides</Emphasis> in the hilly red soil region of southern China

Returning farmland to forests is important for the protection of ecological values. Eucommia ulmoides is considered to be a suitable species for reforestation in the hilly red soil region of southern China. The objective of this study was to investigate the relationship between the water supply and demand of an E. ulmoides plantation to provide insights into the feasibility of large-scale planting for ecological restoration and forest management activities in the hilly red soil region of southern China. With the measured precipitation, surface runoff and interflow and actual evapotranspiration (ET_c) estimated by the modified P–M model, soil water storage (SWS) was estimated based on the water balance equation. Monthly variations of SWS were then compared with in situ measured SWS. The results showed that the estimated mean monthly water losses (the sum of the surface runoff, interflow and ET_c) were 139.8 mm in a wet year and 120.0 mm in a dry year, while the measured mean monthly water input values (net precipitation) were 131.2 mm in a wet year and 70.8 mm in a dry year. Net soil water storage (ΔSWS) was negative in each month of the growing season in a dry year, but the soil water deficit was replenished during the following season. The model performance showed that the modified P–M model can be adapted to estimate the soil water storage in other forest catchments where no adequate in situ data are available. As a result of estimating the water balance and observing soil water storage in two different hydrological years, E. ulmoides is recommended as a suitable forest rehabilitation species in the study area, and a suitable plant region has been defined by the GIS technique based on the water balance model.